Process for the manufacture of phosphatic fertilizer



"UNITED STATES, PATENT OFFICE.

FELIX JOHAN TROMP, OF PRETORIA, TRANSVAAL, SOUTH AFRICA.

PROCESS FOR THE MANUFACTURE F PHOSPHATIC FERTILIZER.

No Drawing.-

To all whom it may concern:

, mineral both with hydrates or-salts of Be it known that FELIX J OHAN TRoMr, a British subject, resi ing' at Transvaal Un1- versity College, Pretoria, Transvaal Province of the Union ofSouth Africa, have invented certain new and useful Improvements in Processes for the Manufacture of Phosphatic Fertilizer, of which the followin' is a specification.

This invention has reference to the treatment of phosphatic'minerals containing 1ron and/or aluminium phosphates, for the pur-' pose of rendering the phosphate contents available for plant life.

It is well known to treat such minerals with hydrates and salts of sodium or potassium for the production of water soluble phosphates, and processes have also been proposed to treat them in various ways with lime for the production of citrate soluble phosphate. It is also known to treat the sodium or potassium and with lime but the processes hitherto proposed in which both these reagents are employed have been costly and efi'ected but a moderate conversion of the phosphateto anassimilable form.

The end product moreover contained such a proportion of alkali compounds as to be injurious to many soils. a

The present invention consists in a wet process employing caustifiable compounds, an alkali, metal and lime, which enables conversions of 90% and over to beattained inparts by weight (reckoned as Na CO to 20 .parts of phosphate (reckoned as P 0 I have found that as ,a rule the best result is obtained when the proportion is about 1 Specification of Letters Patent. Patented )[ar 22 1921. Application filed June 11, 1919. Serial No. 303,427. I

2. The proportion of lime (reclioned as CaO) to phosphate (reckoned as P 0 mustnot be less than 30 to 20. p

In order to obtain the highest conversion it is furthernecessary' that present, it is better to slake the lime beforeparts of water and 2.5 parts of sodium carbonate and heated nearly to the boiling point. 100 parts of powdered quicklime are then added gradually together with sulfioient water to'keep the mass fairly fluid. The mass is kept in vigorous agitation du-r mg the process and about half an hour after the whole of the lime has been addedfthe reaction is completed. The bulk of the water is then removed by evaporation, cenvtrifuglng or the like, and the remaining solid is dried. The product is a citric acid soluble phosphate which can. be applied directly to the land and which can also suc-- cessfully be mixed with other fertilizing agents.

I claiin: 1. A process for the manufacture of citric acid soluble phosphates from iron and/or aluminium phosphates, consisting in treating the'latter with a ca'ustifiablecompound of an alkali metal and lime in. the presence of water, said compound not exceeding 4 equivalehts reckoned as carbonate to 20 parts of phosphate reckoned as phosphoric pentoxid and the lime being not less than 30 3. Caustic and not slaked lime should be toxid.

2. The process as claimed in claim 1, 1n

5 which quicklime is used.

3. The process as claimed in claim 1 in which the lime is added to a mixture of the phosphate, the compound and water.

4. The processas claimed in claim 1 in which the lime is added (with small quantities at a time) to a mixture of the phosphate the compound and water.

5. 'lihe process as claimed in claim 1 in which the treatment is carried out at an elevated temperature,- preferably about boiling polnt.

in testimony whereof I affix my nsi nature.

FELIX JOHAN TRoMP. 

